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Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
I've just done a quick sketch, sorry about the quality, BUT if you incorporate the ducting into the props themselves, you don't actually need to add any weight at all (in fact, you'll probably save some, as you won't need to suppoert the existing ducts).
I realise I'm pretty much repeating what I said earlier, but this would save weight AND increase inertial stability.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Ash Small wrote ...
..., BUT if you incorporate the ducting into the props themselves, you don't actually need to add any weight at all (in fact, you'll probably save some, as you won't need to suppoert the existing ducts).
yes! i was thinking the same thing last night, while sipping the new castle!
Registered Member #2529
Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600
You could also add some stability by adding rod-like structures that don't revolve. Because of the moment of inertia square law thing, you don't need much weight, but the weight must be as far apart as possible. Also moving the rotors further apart should help.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
BigBad wrote ...
You could also add some stability by adding rod-like structures that don't revolve. Because of the moment of inertia square law thing, you don't need much weight, but the weight must be as far apart as possible. Also moving the rotors further apart should help.
yes ive added a wooden dowel across the width of the machine, and that does help, but this machine is already 26 inches wide, and i need it to fit through a 39 inch doorway...
Registered Member #29
Joined: Fri Feb 03 2006, 09:00AM
Location: Hasselt, Belgium
Posts: 500
yes, this is the oblique-active-tilting (OAT) type. the previous version you saw were the FAAT type (fore-aft-active-tilting)... ive had this one 6 feet up totally level and fully controlable, off camera of course! dam it.
Aha! The OAT type system provides the coupling between pitch and roll angle control by its oblique tilting, thereby providing the control authority needed for better stability. The axis coupling provided by the gyroscopic effect in the FAAT version plays the same role.
Great work, btw. I've been lurking in your aircraft related threads for a good while...
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Proud Mary wrote ...
yes ive seen this, its very cool... and the infantry dont have to beg there own side to up a drone, this device would have been useful in Fallujah Iraq, when your storming building after building.
im building both a civilian version (for police, science, academic, fun and corporate purposes) and eventually a martial only version for human erradication... (hope it doesnt go cylon though)
These drones are just too important to get wrong. There are examples of good and poor implimentation. Northrop Grumman lost the YF22-23 compition in the late 80's, they put full effort into the Global Hawk, in 91'. At a time when it wasnt clear at all that drones would have the signifcance they have now.
Meanwhile, Lockheed went fourth, with enormous effort, time and money developing the F-22 which took 20+ years. Now we Americans get much less from the F-22 at much greater cost. (with a pitiful 187 hulls made)
The Global Hawk and Predator B, (Northrop, General Atomics), are far suppioior to the Lockheed RQ170, which was rushed through prouduction, and now is having functional problems, (and apparently "defection to enemy" tendencies.)
I suspect Ben Rich and Kelly Johnson, if alive today, would not be happy with the corporation they did so much for...
There is a lesson for us Americans, somewhere in all this mess, if we bother to learn it.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
i got this reply from Dr. Greg Gress, of Gress Aero Corp.
Patrick,
It's not very effective to add mass so close to the prop centers. Try instead:
- going with heavier props (which you've already done, I believe) - using props with lower pitch (they will have to rotate faster to lift the aircraft) - adjusting the control linkages so the props tilt more for the same servo rotation - carrying more batteries. Increased weight of the aircraft means increased rotational speed and improved gyroscpics.
There might be other things you can do along these lines.
Gary
Quote: Originally Posted by Test Pilot Mafia
Mr Gress,
ive had remarkable progress made with the help of copter ritche and eyeinsky...
id like you to look at this thread (the last page)
im wondering if wrapping lead solder or copper wire around the motor bell will help boost the inertia of the prop and motor combo, thus improving gyro-precession?
TY, Patrick
Wow, i really dropped the intellectual ball on this one!!! his comments are right on, DUH on me !
ive looked at the pitch, since recieving this advice. the MA props i use are a pitch of 7... they only come in 5 or 7 in diameters of 10", i may move up to 11x6x3 MA props, which might be enough change to matter with a stock prop.
New flights and Video:
test flight of brass tipped props.
In this 53 second vid, i have added 400 mircro-grams of brass to each rotor tip, increasing the gyro-precession effect greatly. ive never had this much control, even with the best PID tuning.
Rotors counter-rotate at 6000 rpm, using 10x7x3 Master Airscrew props.
This is an example of the "tail-stall" (followed by dead fish flop-around.)
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